Greek plērōma is simply fullness, the full contents, the patch that completes, the ship's full crew. Paul uses it in Colossians and Ephesians for the fullness of God dwelling in Christ, and the Valentinian system of the 2nd century turned the ordinary noun into the technical name for the entire divine realm: the Father plus thirty aeons in fifteen pairs, the complete and undiminished Godhead, with the boundary, Horos, the limit, guarding it from the deficiency outside. Everything below the Pleroma, the craftsman, the archons, matter, exists because of a subtraction from fullness, Sophia's failed solo creation.
The Valentinian Pleroma's drama is personnel: Sophia, the youngest of the thirty aeons, tries to comprehend the Father's incomprehensibility, strains beyond her capacity, and her botched effort falls outside the boundary as raw material for everything below. Heaven's crisis, in this telling, is an overreach by the newest hire, and the entire material universe is the workplace accident that followed, with the rest of the aeons voting to send a rescuer. The mainstream churches filed this under myth-making; the Valentinians filed the mainstream's simpler story under ignorance of the org chart.
The claim: the Pleroma is antiquity's cleanest model of a closed system that failed, the doctrine that the perfect totality contained the seed of its own breach, nothing added from outside, the youngest member's desire to know the unknowable being the only input, and every modern total system, utopias, platforms, planned economies, sealed ideologies, is a Pleroma with a Sophia somewhere near the bottom of the org chart. Verdict: the system's own logic convicts it: if fullness can leak, it was never full; if it cannot, nothing outside exists to explain. The gnostics solved it with the boundary, a hired limit. Every closed system since has hired the same guard, and the same youngest member is always already curious. The fullness holds. The leak is the world. Do the arithmetic.
If heaven is defined as fullness and the world as what leaked out, what exactly was lost in the leak, and can fullness have a leak?